Picture on the left shows the Calibrated hydrophone just before deployment.
The Graphs: top: Spectrogram showing the sound energy levels at different frequencies that are detected when a ship passes close to the hydrophone; bottom: Try to avoid as there is a noisy gap.
Picture on the far right shows the mooring setup used for deployment. The sub-surface buoy keeps the cable taut so that the hydrophone is always an upright position.
Awareness about the hazard to marine life posed by underwater noise is steadily growing, as are monitoring efforts linked with such an environmental pressure. EU members, including Malta, have an obligation to acquire data under Descriptor 11 – ‘Introduction of energy, including underwater noise is at levels that do not adversely affect the marine environment’ - of the Marine Strategy Framework Directive (MSFD) which includes both impulsive and non-impulsive (continuous) sounds.